This proposed research aims at developing and commercializing a fiber- optic pressure microtransducer (O.3mm x O.3mm x l.Omm, lfrench) that can be integrated in a guide-wire for biomedical applications such as emergency balloon angioplasty. The microstransducer is fabricated using silicon microfabrication methods that allow a D-shaped or side-polished optical fiber to be positioned in close proximity to a silicon pressure- sensing diaphragm with a deposited thin-film optical waveguide. Optical modes supported by both waveguides interact via evanescent wave proximity coupling. Since optical power coupling efficiency from the D-fiber to the thin-film waveguide may decrease by 40dB as waveguide separation increases by lOmu m, the proposed sensor design offers exceptional displacement measurement sensitivity (4dB/mu m) for constructing a sensitive and accurate pressure microtransducer. In Phase I, we seek to demonstrate feasibility and high-sensitivity of the proposed proximity-coupling-based sensing approach. Theoretical models will be developed to predict sensor and waveguide design parameters. Bench tests will be conducted on microfabricated D-fiber and silicon pressure-sensing elements to demonstrate the high sensitivity and validate sensor design. Optimal silicon-fabrication processes, optical-waveguide designs, sensor mechanical parameters, and system optoelectronic parameters will be defined for Phase II prototype sensor-system development.